No abstract

With fused quartz to support polyimide, dense and nanometer-thick carbon films were fabricated by direct laser writing carbonization. Strain-engineering induced micro/nanocrack formation imparts such film with record-high piezoresistive sensitivity.

Direct laser writing carbonization (DLWc) of polyimide has recently emerged as a versatile method for facile fabrication of a variety of functional devices. Up‐to‐date, there is still a lack of comprehensive and in‐depth experimental studies to understand the processing‐structure–property relationship involved in this promising technique. With assistance of methylene blue adsorption as an in situ porous structure characterization method along with scanning electron microscopy, Raman scattering spectroscopy, X‐ray photoelectron spectroscopy, and electrical property measurements, we systematically investigate the multiscale structure evolution and the electrical sheet resistance of the carbon lines fabricated by DLWc at varied laser processing conditions. The key processing parameters being investigated included: laser power (P), laser beam scanning speed (S), distance of laser beam waist to the surface of polyimide film (D), and their combined effect—the averaged areal laser energy density—(E). Quantitative relationships are established between these processing parameters and the specific surface area, the porosity, the degree of perfection of the layered carbon or graphitic basic structure units, as well as the electrical sheet resistance of the carbon lines created by DLWc. The comprehensive and quantitative processing‐multiscale structure–electrical property relationships for DLWc established in this study expect to be useful for better understanding the complicated photo‐thermally induced polyimide pyrolysis/carbonization process.

A nanometer‐thick carbon film with a highly ordered pattern structure is very useful in a variety of applications. However, its large‐scale, high‐throughput, and low‐cost fabrication is still a great challenge. Herein, microcontact printing (µCP) and direct laser writing carbonization (DLWc) are combined to develop a novel method that enables ease of fabrication of nanometer‐thick and regularly patterned carbon disk arrays (CDAs) and holey carbon films (HCFs) from a pyromellitic dianhydride‐oxydianiline‐based polyamic acid (PAA) solution. The effect of PAA concentration and pillar lattice structure of the polydimethyl siloxane stamp are systematically studied for their influence on the geometrical parameter, surface morphology, and chemical structure of the finally achieved CDAs and HCFs. Within the PAA concentration being investigated, the averaged thickness of CDAs and HCFs can be tailored in a range from a few tens to a few hundred of nanometers. The µCP+DLWc‐enabled electrically conductive CDAs and HCFs possess the characteristics of ease‐of‐fabrication, nanometer‐thickness, highly regular and controlled patterns and structures, and the ability to form on both hard and soft substrates, which imparts usefulness in electronics, photonics, energy storage, catalysis, tissue engineering, as well as physical, chemical, and bio‐sensing applications.